Starting unloader for multistage compressors



March 29,1938. H v. HAIGHT STARTING UNLOADER FOR MULTISTAGE COMPRESSORS Filed NOV. 11, 1935 2 Sheets-Sheet l INVENTOR Hair [[17 {flit BY I HIS ATTORNEY- March 29, 1938. K H, v. HAIGHT 2,112,564

- STARTING UNLOADER FOR MULTISTAGE COMPRESSORS Filed Nov. 11,1935" 2Sheet'sSheet 2 fw/XW 3 4.9 40

41 4 1 I E15 13. J 5 pfiz'wfl BY HIS ATTORNEY.

Patented Mai-.29, 1938 UNITED STATES PATENT OFFICE STAB.TING UNLOADER FOR M'UL'I'ISTAGE COMPRESSORS Harry V. Haight, Ashton-on-Mersey, England;

asslgnor to Ingerso City, N. J., a corpora -Rand Company,

Jersey tion of New Jersey Application November 11, 1935, Serial No. 49,207

1 Claim.

This invention relates to compressors, but more particularly to an unloader fo'r compressors .of the multi-stage type.

Other objectsv will be in part obvious and in Part pointed out hereinafter.

In the drawings accompanying this. specification and in which similar reference numerals refer to similar parts, 15 Figure 1 is an end elevation of a compressor equipped with'an unloader constructed in accordance with the practice of the invention,

Figure 2 is a side elevation of the compressor partly broken away. and

Figure 3 is an elevation, in section, of the unloader.

Upon being compressed to a higher 46 pressure in the latter cylinder the fluid passes through a discharge conduit 33 into a storage receiver 3|. i

In accordance with the present invention,

means are provided for relieving the motor26 L from the strain of starting the compressor when of the diaphragm is a plate pressure cylinder 23.

' opening of the tubular member daubuiar member 32 of which the interior or passage 33 serves to convey fluid from the manifold.

The'tubuiar member 32 supports a valve'mech-, anism 34 of which a casing 35 is threadedly connected to an intermediate portion of the tubular member. The lower end 36 of the member 32 projects into a chamber 31 in the casing 35, and in the side of the chamber 31. is an outlet-opening, illustrated as being in the form of a conduit 33, which may open directly to the atmos- Dhere-or to a source of fluid medium.

The casing 35 consists of an upper section 33 threaded to the tubular member 32 and a lower section 40 secured to the section 39, as by bolts 4|. A flexible diaphragm 42 is clamped between the casing sections to seal the chamber 31 from a chamber 43 in the casing section.

The diaphragm 42, which may be capable of a considerable degree of movement in the casing 35, carries avalve 44 to control the outlet opening of the passage 33. The valve is secured to the diaphragm by a bolt 45. It is arranged in a plate 46 upon which-is seateda spring 4! arranged about the lower end 36 of the tubular 4 member to open the valve. On the lower surface 48 which is clamped to the diaphragm by the bolt 45 and seats against a hollow boss 49 in the chamber 43 for limiting the opening movement of thevalve 44.

The surface of the diaphragm confronting the chamber 43 constitutes a pressure surface 53 which is subjected to pressure fluid admitted to the pressure chamber 43 directly from the high Such pressure fluid is conveyed to the chamber 43 by a conduit 5| which communicates constantly with the upper'end of the high pressure cylinder 23 through a passage 52 and with the chamber 43 through a port 53. Thus, in operation, pressure fluid may flow directly from the high pressure cylinder 23 through the conduit 5| into the chamber 43 and act against the pressure surface. for holding the valve'44 in sealing relationship with the outlet 32 to normally prevent the flow oi the lower stage discharge 45 pressure to the atmosphere.

In order, however, to assure the retention of a suitable pressure in the provided with a. delay valve mechanism 54 com- 55 p -is that ofa --ing prising a casing '55 into the ends of which are threaded sectionsof the conduit 5|.

Within the casing 55 are a pair of passages 56 and 51 of which the passage 5i is in direct communication with a portion of the conduit Bl connected to the chamber 43, and the passage 51 communicates directly with the conduit leading to the high pressure cylinder 23. The passages 56 and 51 communicate with each other through ports 58 and 59. The function of the port 58 discharge port for the passage 51 and said port is controlled by a check valve 80 arranged in a recess 6| at'the outlet end of the port 5l. The opening movement of the valve 60 is resisted by a spring 62 extending into and guided by a bushing 63 threaded into the casing 55.

The-port 59 serves as a' passage 56. tapered portion 64 to conform to the end of a needle valve 65 extending thereinto to define the flow area of the port 59. The needle valve is threaded into the casing 55 and lockedin position, in the present instance, by a cap nut 66 whichseats against'the side of the casing 55 to prevent loss of pressure fluid along the threads of the needle valve to the atmosphere.

Any suitable means may be employedfor the conduit 5| to the atmosphere or a source of fluid medium in order to provide an escape for pressure fluid from the chamber 43 and from the cylinder 23 at the end of an operating period in order to relieve the compressor of its load for a subsequent period of operation. The means illustrated for this. purpose comprises a valve cage 61 to which is connected a branch of the conduit 5i and containing a ball valve SI for controlling a discharge port 09 in the valve cage. The valve cage is preferably arranged concentrically with respect to the crank shaft 25 of the compressor and in the end of the drive shaft is a plunger Ill having a reduced projection ll which extends loosely into the port 69 to unseat the ball valve '8. The plunger to perform this function, by a spring 12 and is normally held in retracted position by centrifugal weights 13 mounted on pivots 14 carried by the crank shaft 25.

The operation of the device is as follows:

that the plunger III is then actuated, by the spring 12 to unseat the valve 68. With the ball valve in this position the high pressure cylinder 23 and the chamber 43 will be in direct communication with the atmosphere. The valve 44 will then be held in its open position by the spring discharge port for the Its inlet end is in the form of .a I

ventthe ball valve 3, The

10 is actuated,

Let it be assumed that the compressor is at rest and the fluid medium entering the high pressure cylinder may escape through the conduit ii, the valve cage 61 and through the port 69 to its source. The compressor will continue to operate in this wise until its speed approaches or reaches normal, at which time the centrifugal action of the weight 13, retracts the plunger Ill and the ball valve 63 will thenclose the port 69 to prevent further passage of fluid to the atmosphere.

Thereafter, the fluid compressed in the high pressure cylinder 23 flows through the conduit II, passage 51, port 58 and the passage 56 into the chamber 42 and shifts the valve 44 into sealing relationship with the end of the tubular 1 member 32. The manifold and inter-cooler will then be closed and the fluid compressed by-the to allow only a very considerably restricted flow of pressure fluid through the port 59.

when the compressor again ceases operating the spring 12 actuates the plunger I. and unseats high pressure cylinder will then again be communicated with the atmosphere, and the pressure fluidin the chamber 43 employed for holding the valve I closed flowsfrom the chamber 43 through the passage 56, the space defined by the needle valve and the portion 84, thence through the valve cage 61 tothe atmosphereto again completely unload the inter-cooler and also the high pressure cylinder 23 preparatory to another period of operation.

I claim: A starting unloader for a compressor having I a cylinder operating-ata low pressure and a cylinder operating at a higher pressure, an intercooler between the cylinders and having an atmospheric vent, a pressure actuated valve to control the vent, a conduit leading from the high pressure cylinder on the cylinder side of the discharge valve in constant communication with the high pressure cylinder, means in the conduit between the high pressure cylinder and the inter-cooler for venting the valve and the high pressure cylinder to the atmosphere for unloading the compressor,

and means between the venting means and the valve for restricting the flow of pressureifluid from the valve to the venting means while permitting free flow offluid from the high pressure cylinder to the valve.

HARRY V. HAIGHT.

thereof to the valve and being 

